The instant invention pertains to methods and apparatus for calibrating a material-spreading applicator (also referred to as a spreader) and more particularly to such methods and apparatus for calibrating applicators of the type which spread material on a surface as the applicator moves thereover.
Applicators which spread material on a surface are used in farming to spread seed, pesticide, and fertilizers on a field. Such agricultural applicators are typically loaded with the material to be distributed and hitched to a tractor. The applicator includes a control which dispenses the material at a selected rate as the tractor pulls the applicator over the field. Optimum applications, in total quantity per unit field area, for different materials are known, for example, fifteen to twenty-five pounds of alfalfa per acre; one to two pounds of small hog clover per acre; and forty-five to seventy-five pounds per acre of field beans are the ranges of optimum applications for these particular crops. The foregoing crops are planted in rows having a preselected width between one another. The applicators which are used to spread these seeds do so in evenly-spaced rows having a pre-selected distance therebetween.
Other types of material, typically fertilizer and pesticide, are intended to be uniformly or broadcast spread over the entire field. As in the case of seed spreading, each different type of fertilizer or pesticide has a recommended quantity per acre at which it should be applied to a field. Broadcast spreaders, like row spreaders, include a control for varying the quantity per acre at which material is distributed.
The control, on both broadcast and row spreaders, for varying the rate at which material is spread on the field as the applicator moves is typically a lever having a numerical scale for indicating relative lever positions. The scale generally does not indicate quantity per acre of material spread because the density of materials to be spread varies and thus the applicator must be calibrated for each type of material. Moreover, because even the same material can vary slightly in density and because of the inexact nature of the controls on most applicators, it is desirable to calibrate the applicator each time material is spread.
There exists a prior art method for calibrating a row spreader in which the spreader is pulled for a measured length and the material which would have been spread over the measured length is caught. The volume of the caught material is determined and a graph is used to determine the pounds per acre at which the material is spread when the row width, material volume spread per foot of row length, and pounds per bushel of the material is known. The pounds per bushel is determined by reference to a chart.
The above-described prior art method suffers from several disadvantages. First, since the density of material may vary, use of a single assigned density for a given material injects error into the calibration procedure. Secondly, the density of material being spread must be known. Also, the prior art method cannot be used to calibrate materials such as pesticide and fertilizer which are typically broadcast spread.
The present invention provides a method and apparatus for calibrating broadcast and row spreaders. The spreader is moved over a surface for a measured length and the amount of material which it would have spread while it was so moved is caught. The area on which the caught material would have been spread while the applicator was so moved is calculated and the caught material is weighed. Dividing the weight of the caught material by the calculated area produces the application rate of the material.
In another aspect of the invention, apparatus for weighing the material is provided which includes an elongate arm having a weight slidable therealong. A container is mounted on one end of the arm and is conical in shape. A support is pivotally attached to the arm between the container and the weight and is used to suspend the arm when material is placed in the container for weighing. The apparatus may also be used to determine the density of a material.